It is usually much less expensive to get the leaders of a country to support US policy by bribing them than with military power, and if the leaders can't be bribed then the money can be used to install leaders who can.

Is this surprising at all? The first thing Karzai did on his first name in office was to allow the oil piepline to be built across Afghanistan that the oil companies were clamoring for for years, but were denied by the Taliban

The CIA really struggled for a while after the end of the Cold War. We no longer had a major enemy, so their importance and prestige dwindled significantly.

Then 9/11 happened, and they've enjoyed a rebirth of importance and the boon of the Patriot Act making their jobs easier than ever before. Combined with precisely zero accountability, they've been free to do whatever they wanted.

It's not at all surprising that bribery was a major part of it, since that's pretty much the main way all foreign nations gain influence in third-world hellholes like Afghanistan.